It's selling for 50% off (that's only $19.99) starting today on both Microsoft's Games on Demand and Stardock's Impulse! 

This is a deal way too good to pass up if you haven't played the game yet, or even if you have it on console, you can crank all your settings and get some truly amazing details, not to mention the special graphical filters (oh and also you can actually use it to play Street Fighter IV, if that's your cup of tea). 

Sale ends Monday in both places, so get it NOW.  Please :)